Vehicle bumpers may have a stiffness determined by the material and structure of the bumper. However, the desired stiffness of the bumper may be different depending on vehicle speed. For example, at a low vehicle speed, a higher stiffness may be desired to prevent damage to the bumper, while at a high vehicle speed, a lower stiffness may be desired to absorb energy during a pedestrian or vehicle impact.
Several vehicle research organizations release test protocols and standards for vehicles directed to specific outcomes. For example, the Research Council for Automobile Repairs (RCAR) releases impact test protocols and standards for vehicles. One example RCAR impact test protocol is directed toward low speed damageability (LSD), i.e., damage to vehicle component at 15 kilometers per hour (kph). In another example, the National Highway Traffic Safety Administration (NHTSA) releases the Federal Motor Vehicle Safety Standards (FMVSS) Part 581, which describes impact test protocols for LSD of vehicle bumper systems. Other regulations for LSD include 49 CFR Part 581 (USA), ECE 42 (Europe), GS 41 (GCC), Article 93 (Korea), and CMVSS 215 (Canada, 5 mph). However, as described above, the stiffness of the bumper system for LSD may differ from the stiffness desired for pedestrian protection. For example, the European New Car Assessment Programme (EURO NCAP) protocols for upper leg impact at 40 kph and lower leg impact at 40 kph may be benefited by a lower stiffness for the bumper in comparison to the stiffness desired for FMVSS protocols for LSD. In other words, requirements for LSD and pedestrian protection may create competing design principles. There remains an opportunity to design a vehicle bumper that accounts for low speed damageability and pedestrian impact.